The field of the invention is expandable batons, or night sticks and, more particularly, to expandable batons which comprise two or more rigid telescoping sections. This invention is also directed to a method of manufacture for the aforementioned expandable batons.
Expandable batons are commonly used by policemen as an alternative to fixed length, one piece night sticks. The latter are usually made of hardwood and measure approximately 26 inches long by 11/4 inch in diameter. Expandable batons are preferred because they are more convenient to carry than one piece night sticks. The expandable baton includes a hollow main section which serves as a handle. Each of the telescoping sections has a diameter progressively smaller than the inside of the handle. When collapsed, the telescoping sections are nested inside the handle.
Expandable batons come in a variety of sizes, but usually consists of three telescoping sections. The longest sizes of expandable batons extend to a length comparable to a one piece night stick. In the closed position, a three section expandable baton is just over one third of its extended length, owing to the overlap of the section.
Shorter expandable batons are also available for even greater carrying convenience at the expense of extended length. Such a short baton might measure, for example, six inches in length closed and 16 inches extended.
To be effective, the expandable baton must be capable of being extended and locked in place very quickly and simply. This is because the baton may be needed suddenly and in a crisis situation. The most common mechanism for locking the telescoping sections in place is a deadlock taper joint, comprising a swage on one end of an outer telescoping section and a mating flare on an inner telescoping section. In that case, the baton is simply extended by sharply swinging the handle in an arc. Doing so causes the inner telescoping sections to be thrust outward by centrifugal force, until the flares and swages engage. When swung hard enough, the sections are locked together so tightly that only a sharp axial blow on a very hard object, for example, a concrete wall or pavement, can break the deadlock joint between sections.
However, prior expandable batons have failed to gain widespread popularity, primarily because of manufacturing tradeoffs that had been necessary in their construction. Specifically, it was first desired to use relatively soft steel for the handle and telescoping sections to facilitate the swaging and flaring operations. This results in ease of manufacture and a corresponding low cost. While such batons continue to be manufactured, they suffer a serious drawback. While soft steel is easily worked, it is also relatively weak. When the telescoping sections are locked together there is a tremendous amount of stress at the joints, both from the locking tension and bending moments during use. Batons made of soft steel are therefore highly prone to separation at the joints. In fact, telescoping sections have been known to literally "fly apart" during the extension thrust as the soft metal of the swedge opens up and the soft metal of the flare collapses, thereby allowing the inner section to pass straight through the outer section at the joint.
Because of the circumstances under which expandable batons are used, the degree of unreliability imparted by the use of soft steel in their construction is totally unacceptable. Attempts have been made to produce batons from harder steels. Such batons perform satisfactorily, but are extremely expensive to manufacture. Special tooling is required and the service life of such tooling is reduced in working with hardened steels. Also, the rejection rate is high due to brittleness of the hardened steel as it is swaged and flared. In the finished expandable baton, this brittle steel tends to crack, allowing the same straight through separation as previously discussed.